The purpose of the proposed project is to study the relationship between intestinal lymph flow, lymph pressure, and fluid transport under various experimental conditions in rats, cats or dogs. The results to be obtained would further the understanding of the fundamental mechanisms involved in fluid absorption or secretion in various pathophysiological states, and could lead to the development of more effective treatment for various diseases involving malabsorption or fluid loss from the intestine such as in hemorrhagic shock, various diarrheal states including cholera, or intestinal obstruction. A new in vivo intestinal preparation developed in this laboratory will be used, except that in larger animals (cats and dogs) lymph flow from both mesenteric lacteal ducts (pre-nodal) and the main intestinal lymph duct (post-nodal) will be determined. Hydrostatic pressure in the mesenteric lacteal duct and the main intestinal duct will be measured. The animals will be under pentobarbital anesthesia.